Rihanna‘s summer tour got off to a slow start when her opening show on July 2 was canned, delaying the tour’s launch until the...

Rihanna‘s summer tour got off to a slow start when her opening show on July 2 was canned, delaying the tour’s launch until the July 4 show in Vancouver, BC. Now the Last Girl on Earth Tour, featuring support from pop party girl Ke$ha, has suffered more cuts from its calendar.

Trimmed from the schedule are shows on July 15 at Comfort Dental Amphitheatre in Englewood, CO; July 24 at Superpages.com Center in Dallas, TX; July 28 at Philips Arena in Atlanta, GA; and August 3 at Verizon Wireless Music Center in Noblesville, IN.

Brief notations on Live Nation’s ticket listings for Englewood and Noblesville noted that the singer is unable to appear in those cities due to a “change in schedule.” Details were not provided for the other axed dates; refunds will be distributed from the original point of purchase.

Last month, Rihanna’s July 22 concert — originally scheduled for the Cricket Wireless Pavilion in Phoenix, AZ — was moved to the significantly smaller AVA Amphitheater at Casino de Sol in Tucson, AZ. Tickets for the 20,000-capacity Pavilion had ranged from $25.75 up to $95.75, according to Live Nation. Prices for the performance in the 5,000-capacity AVA range from $60 to $125.

In Tuscon, tickets for front reserved seats are sold-out, and only a handful remain unsold in the rear of the amphitheater, according to seat maps on the venue’s official Web site. While 2,000 general admission lawn tickets are still available, Rihanna’s upcoming concert is faring much better than Robert Plant (July 21) and Cyndi Lauper (August 15), both of whom have much larger blocks of reserved seating available at the venue.

The Last Girl on Earth Tour continues with a July 14 show at The Pavilion in Albuquerque, NM. As it stands now, Rihanna’s itinerary concludes with a performance at the Great New York State Fair on August 28 in Syracuse, NY.

Rihanna’s original tour itinerary can be reviewed here.